1. Field of the Invention
The present invention relates to a client server system.
2. Description of Related Art
A client server system has been conventionally known which can transmit video data reproduced with audio-video (AV) equipment (digital versatile disc (DVD)/hard disk drive (HDD) reproduction unit and the like) installed in a server apparatus from the server apparatus to a client terminal apparatus by wireless communication to output the transmitted video data to an output unit installed in the client terminal apparatus. In the client server system of this sort, because the video data is transmitted by wireless communication, the client server system has a problem of the occurrence of a transmission delay. Moreover, the video data is sometimes output to the output unit after being stored in a buffer installed in the client terminal apparatus in preparation for interruption of transmission or for convenience of processing, and there exists a problem of the occurrence of a further time lag from the reproduction of the video data to the output thereof.
For instance, as shown in FIG. 7, video data a, b, c . . . reproduced by the AV equipment is wirelessly transmitted to the client terminal apparatus, and stored in the buffer. After that, the video data a, b, c . . . is output to the output unit.
To put it concretely, for example, at a time point [t13], the AV equipment reproduces the video data k in a fast-forward reproduction mode; the buffer stores the video data h reproduced by the AV equipment at a time point [t12]; and the output unit outputs the video data e, which has been reproduced at a time point [t11] by the AV equipment and stored in the buffer at the time point [t12].
It is assumed that a signal instructing a selection of a normal reproduction mode as a reproduction mode of the AV equipment is transmitted from a remote controller (hereinafter referred to as a “remote control”) for the server apparatus, which remote control is operated by a user at the time point [t13] in the reproduction operation by the AV equipment in the fast-forward reproduction mode. That is, it is supposed that the user wants to watch the video based on the video data following the video data e (the video data on and after the video data f) in the normal reproduction mode. The server apparatus, which has received the signal transmitted from the remote control, controls the AV equipment to change the reproduction mode thereof from the fast-forward reproduction mode to the normal reproduction mode. That is, because the AV equipment changes its reproduction mode to the normal reproduction mode immediately after the time point [t13], the AV equipment reproduces the video data on and after the video data 1 in the normal reproduction mode. Consequently, there is a problem in which the video data desired by the user (the video data on and after the video data f) cannot be reproduced in the reproduction mode desired by the user (normal reproduction mode).
Accordingly, a method of adding time information to video data was proposed for instance (see, for instance, JP 2003-209810A).
To put it concretely, for instance, a server apparatus (a moving video transmission apparatus) adds the time information (counter values or the like) to the video data reproduced by AV equipment (video reproduction means), and transmits the time information-added video data to a client terminal apparatus (video reception means). Then, when a remote control for the client terminal apparatus is operated by a user to instruct a switch of the reproduction mode of the video data, the client terminal apparatus acquires the time information from the video data output at the time point of the instruction by an output unit (video display means) to transmit the time information to the server apparatus. The server apparatus calculates the quantity of the video data to be returned, and makes the AV equipment reproduce the video data from the point corresponding to the return quantity.
Furthermore, for instance, in the case where a reproduction start position of video data was specified by the operation of a slider displayed on an output unit, a method of associating a shifting quantity of the knob of the slider with the video data was proposed (see, for instance, JP Hei 11-127420A). To put it concretely, still image data of the video data having smaller quantity of data than that of the video data has been associated with the shifting quantity of the knob of the slider to be stored in a server apparatus (video transmitter) in advance. Then, when a user specifies a reproduction start position of the video data by moving the knob of the slider displayed on the output unit (an video and sound output unit), the client terminal apparatus (the video receiver) transmits the shifting quantity of the knob to the server apparatus. The server apparatus acquires the still image data equivalent to the transmitted shifting quantity of the knob out of the stored still image data to transmit the acquired still image data to the client terminal apparatus, and begins the reproduction of the video data from the position corresponding to the still image data.
Moreover, a method of making an output unit output a still image when a pause was instructed, for instance, was also proposed (see, for instance, JP 2002-291065A).
To put it concretely, for instance, when a user operates a remote control for a client terminal apparatus (a reception unit) to instruct a pause of an video based on video data, which video is output by an output unit (a liquid crystal monitor), the client terminal apparatus transmits the instruction to a server apparatus (a transmission unit), and makes the output unit output the still image based on the video data output at the time point of the instruction.
Moreover, a method of not settling any transmission delay owing to wireless communication but of settling a delay of AV equipment (a compressed video reproduction apparatus) at the time of compressed video data reproduction after performing fast-forwarding or rewinding was also proposed (see, for instance, JP Hei 8-107540A).
However, it is necessary to perform Moving Picture Experts Group (MPEG) coding processing to video data to add time information to the video data like the method of, for instance, JP 2003-209810A. That is, the method of JP 2003-209810A is effective only when video data is coded by MPEG coding and transmitted.
Moreover, the method of JP Hei 11-127420A is effective only when a reproduction start position of video data is specified with the slider.
Furthermore, the method of, for instance, JP 2002-291065A is effective only when a pause instruction is issued.
Moreover, the method of, for instance, JP Hei 8-107540A is effective only when video data is not transmitted by wireless communication.
Consequently, any of the methods disclosed in JP 2003-209810A, JP Hei 11-127420A, JP 2002-291065A and JP 8-107540A are effective only in limited cases, and their uses are limited.